Transverse partition for exhaust volume

ABSTRACT

The transverse partition for separating an exhaust volume into two adjacent chambers includes at least one gas flow passage between the two chambers, the gas flow section through the passage being modifiable under drive from the difference between the pressures on the two sides of the partition. The partition comprises a wall pierced by at least one slit defined between two adjacent edges of the wall, which wall is elastically deformable under drive from the difference between the pressures on the two sides of the partition, between a rest position in which wall continuity is ensured, the two edges of the slit being substantially touching, and a deformed position in which the two edges of the slit are spaced apart so as to define said gas-flow passage between them.

The present invention relates to a transverse partition for separatingan exhaust volume into two adjacent chambers, the partition being of thetype comprising at least one passage for allowing gas to flow betweenthe two chambers, the gas flow section through the passage beingmodifiable under drive from the difference between the pressures on thetwo sides of the partition.

BACKGROUND OF THE INVENTION

In exhaust mufflers, it is known to define two adjacent chambers thatare separated by a transverse partition, the chambers being capable ofbeing put into communication with each other automatically at highengine revolutions.

For this purpose, a flap valve is installed on the transverse partitionextending across the exhaust muffler and separating the two adjacentchambers.

By way of example, such a valve is described in Japanese patentapplication JP-08004990. That valve comprises a seat defining a gas flowpassage and a flap hinged to an edge of the seat. The flap can be movedbetween a closed position where it bears against the seat and a positionin which it is spaced apart from the seat allowing gas to flow freely. Aspring is provided to urge the flap towards its closed position. Theflap is moved away from the seat under drive from the difference betweenthe pressures in the two chambers.

The valve structure described in that document is very complex and itincorporates a large number of parts, thereby considerably increasingthe cost of manufacturing an exhaust muffler that incorporates it.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the invention is to propose a transverse partition for anexhaust volume that allows gas to pass through in controlled manner andthat can be manufactured at very low cost, and also to propose anexhaust muffler incorporating it.

To this end, the invention provides a transverse partition of theabove-specified type for separating an exhaust volume into two adjacentchambers, the partition comprising a wall pierced by at least one slitdefined between two adjacent edges of the wall, which wall iselastically deformable under drive from the pressure difference betweenthe two sides of the partition, between a rest position in which wallcontinuity is ensured, the two edges of the slit being substantiallytouching, and a deformed position in which the two edges of the slit arespaced apart so as to define said gas flow passage between them.

In particular embodiments, the partition includes one or more of thefollowing characteristics:

said wall is generally plane;

said slit is generally spiral-shaped;

said wall is generally cylindrical;

said slit is generally helically shaped;

said generally cylindrical wall is closed at one of its ends;

the partition comprises a generally plane main panel, and said generallycylindrical wall extends perpendicularly to said panel;

one of the surfaces of the generally cylindrical wall is covered by agas-permeable sheath, in particular a braid;

said slit is wound around at least two turns;

the thickness of the region of the wall in which the slit is defined isgreater than the average thickness of said partition; and

the thickness of the wall region where the slit is defined is greaterthan the average thickness of said partition.

The invention also provides an exhaust muffler defining an enclosure andincluding at least one transverse partition as defined above, saidpartition defining two adjacent chambers within the enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on reading the followingdescription given purely by way of example and made with reference tothe drawings, in which:

FIG. 1 is a perspective view of an exhaust muffler of the invention;

FIG. 2 is a perspective view of the intermediate partition of the FIG. 1muffler, the partition being shown at rest;

FIG. 3 is a view analogous to FIG. 1 showing the same intermediatepartition, the partition being shown elastically deformed under drivefrom a pressure difference between its two faces;

FIG. 4 is a perspective view of a variant embodiment of the intermediatepartition, the partition being shown at rest; and

FIG. 5 is a perspective view of the FIG. 4 partition shown deformedunder drive from a pressure difference between its two faces.

MORE DETAILED DESCRIPTION

The exhaust muffler shown in FIG. 1 comprises an exhaust volume 12, agas feed tube 14, and a gas exhaust tube 16. The volume 12 comprises agenerally cylindrical case 18 closed at each end by an end wall 20, 22.The tubes 14 and 16 pass through the end walls 20 and 22 and projectinto the inside of the exhaust volume.

The volume 12 also has an intermediate partition 24 extendingtransversely and defining two adjacent chambers 26 and 28 inside thevolume 12.

Such a transverse partition can also be referred to as a “cup”.

FIG. 2 shows the partition 24 at rest. It comprises a plane main wall 30in the form of a disk surrounded by a peripheral rim 32 enabling theintermediate partition 24 to be secured to the casing 18 of the exhaustvolume.

The main wall 30 is pierced by two openings 34, 36 each serving to passone of the tubes 14 and 16. Thus, each tube passes through theintermediate partition 24 and opens out into a chamber of the exhaustvolume after passing right through the adjacent chamber.

The running portions of the tubes 14 and 16 are provided with side slots38 that open out into the chambers which they pass right through.

In its central region, the main wall 30 is pierced by at least one slit40 made in an elastically deformable region of the wall.

The region where the slit 40 is formed can be of thickness that isdifferent from the average thickness of the wall 30, which in thisexample means the major portion of the partition. Advantageously, thethickness of the region where the slit is formed is greater than theaverage thickness of the wall. The values of these thicknesses can liein the range 0.4 millimeters (mm) to 2 mm. For example, the wall 30 canbe made of steel. The thickness of the wall in the region where the slitis formed can be 1 mm while its thickness outside the region in whichthe slit is formed can be 0.5 mm.

In an embodiment that is not shown, the region where the slit 40 isformed can be constituted by an extra part. This part is secured to thewall 30 by any means of appropriate type, e.g. rivets.

In the embodiment shown in FIG. 2, the slit 40 is generally spiralshaped. It is wound over about five turns. The slit is woundadvantageously over more than one turn. The slit 40 thus defines aspiral-shaped strip 42 in the central portion of the wall 30 andextended in its central portion by a disk 43 formed integrallytherewith.

Advantageously, the slit 40 is made by laser cutting. It could also beformed by punching.

The slit 40 is of small width, such that the two edges defining the slitlie in the immediate vicinity of each other when the partition 24 is atrest, i.e. when it is not being stressed by a difference in pressurebetween its two faces. Under such conditions, the spiral shape 42 liesin the main plane of the wall 30 thus forming a substantially solidscreen presenting very little leakage between the two chambers of theexhaust volume, with the edges of the slit 40 then being substantiallyadjacent.

In contrast, when a significant pressure difference exists between thechambers 26 and 28, the spiral strip 42 is stretched by elasticdeformation as shown in FIG. 3. The strip deforms in a direction that issubstantially perpendicular to the plane of the wall 30. The edgesdefining the slit 40 are then spaced apart leaving between them apassage 44 that allows gas to flow from one chamber to the other.

Once the pressures in the two chambers 26 and 28 have come intoequilibrium, the elastically deformed region of the wall returns to itsposition shown in FIG. 2 under drive from the elasticity of the spiralshape 42. In this position, continuity of the solid wall 20 is provided.

In another variant, resilient means are associated with the spiral strip42 so as to assist it returning to its initial position once pressurehas moved into equilibrium. Advantageously, the resilient means areconstituted by a spring having one end secured to the disk 43 and asecond end secured to the end wall 22. The person skilled in the art candefine suitable characteristics for the spring, and in particular itsstiffness. In this embodiment, the spring is sheltered from the hightemperature gas flow and serves to guarantee increased lifetime for thedevice of the invention.

It will be understood that using a deformable region defined by a slitthrough the wall 30 makes it possible to ensure that gas flows incontrolled manner between the two chambers, with such flow beingpossible only if a sufficient pressure difference exists between the twochambers. In addition, this gas flow control can be obtained at amanufacturing cost that is very low since there is no need to add anyparticular elements into the exhaust volume.

FIGS. 4 and 5 show another embodiment of a transverse partition 124 thatcan be implemented in the exhaust muffler of FIG. 1 by replacing theintermediate partition 24. In this embodiment, elements which areidentical or analogous to those of the embodiment shown in FIGS. 2 and 3are given the same reference numerals plus 100.

Thus, the transverse partition 124 has a main panel 130 in the form of adisk with a surrounding rim 132 and it is provided with two openings 134and 136 for passing tubes 14 and 16. In its central portion, the panel130 has a third opening of circular section 150 with a tube 152 fittedto the perimeter thereof, which tube is defined by a cylindrical wall154. The tube 152 is of circular section. In a variant, its circularsection could be of varying radius or its section could be elliptical.It presents an axis X—X extending perpendicularly to the panel 130. Thetube is made of an elastically deformable material, e.g. a steel of theInconel (registered trademark) type or a stainless steel having athickness of 0.8 mm. In contrast, the thickness of the main panel 130 is0.5 mm.

The tube 152 is crimped at one end to the surface of the panel 130.Thus, it extends on one side only of the panel 130. At its free end, thetube 152 is closed by a stopper 156 which is constituted in this case bya disk welded thereto.

Over the major part of its length, the cylindrical wall 154 presents aslit 160. This slit is helically shaped. It extends over some number ofturns that is greater than two, and which is equal to twelve, forexample. The slit thus defines turns 162 along the tube.

At rest, as shown in FIG. 4, the edges defining the slit 160 aretouching so that the wall 154 defines a continuous surface forming anessentially gastight barrier between the two chambers of the exhaustmuffler. The turns 162 then touch one another.

In contrast, when the pressure in the chamber communicating with theinside of the tube 152 increases, then the wall 154 expands underelastic deformation and the initially touching edges of the slit 160move apart from one another so as to define a gas flow passage 164 whichis helical in shape. The turns 162 are then no longer touching.

After pressure has returned to equilibrium in the two chambers, thecylindrical wall 154 returns to its initial shape under drive from theelasticity of the wall 154. The turns 162 defined by the slit 160 arethen touching.

In a variant, a gas-permeable sheath 166 is fitted over the majorfraction of the surface of the tube 152 in contact with one and/or theother of the surfaces of the cylindrical wall 152. In an additionalvariant (not shown), the sheath 166 is fitted to the surface of theturns 162. By way of example, the sheath can be made of a metal braid ora composite material braid. Such a sheath is represented by chain-dottedlines in FIGS. 4 and 5.

The presence of this sheath reduces the noise that results from gasflowing in the tube.

In an additional variant, resilient means are associated with the tube152 for assisting it back into its initial shape after pressures havereturned to equilibrium. Advantageously, the resilient means areconstituted by a spring secured via a first end to the stopper 156 andvia its second end to the end wall 22. The person skilled in the artknows how to define suitable characteristics for the spring, and inparticular its stiffness. In this embodiment, the spring which issheltered from any high temperature gas flow serves to provide longerlifetime for the device of the invention.

What is claimed is:
 1. A transverse partition for separating an exhaustvolume into two adjacent chambers, the partition being of the typecomprising at least one passage for allowing gas to flow between the twochambers, the gas flow section through the passage being modifiableunder drive from the difference between the pressures on the two sidesof the partition, the partition comprising a wall pierced by at leastone slit defined between two adjacent edges of the wall, which wall iselastically deformable under drive from the pressure difference betweenthe two sides of the partition, between a rest position in which wallcontinuity is ensured, the two edges of the slit being substantiallytouching, and a deformed position in which the two edges of the slit arespaced apart so as to define said gas flow passage between them, whereinthe thickness of the region of the wall in which the slit is defined isgreater than the average thickness of said partition.
 2. A partitionaccording to claim 1, wherein said wall is generally plane.
 3. Apartition according to claim 2, wherein said slit is generallyspiral-shaped.
 4. A partition according to claim 3, wherein said slit iswound around at least two turns.
 5. A partition according to claim 1,wherein said wall is generally cylindrical.
 6. A partition according toclaim 5, wherein said slit is generally helically shaped.
 7. A partitionaccording to claim 5, wherein said generally cylindrical wall is closedat one of its ends.
 8. A partition according to claim 5, comprising agenerally plane main panel, and wherein said generally cylindrical wallextends perpendicularly to said panel.
 9. A partition according to claim5, wherein one of the surfaces of the generally cylindrical wall iscovered by a gas-permeable sheath, in particular a braid.
 10. An exhaustvolume defining an enclosure and including at least one partition inaccordance with claim 1, which partition defines two adjacent chamberswithin the enclosure.
 11. The partition according to claim 1, whereinsaid region in which said slit is defined is smaller than a majorportion of said wall.
 12. The partition according to claim 11, whereinsaid thickness of said region and said average thickness lie in therange of 0.4 mm to 2 mm.
 13. The partition according to claim 12,wherein the thickness of said wall in said region is 1 mm. and whereinsaid major portion has a thickness of 0.5 mm.